Geochemistry of Metal and Metalloid Thioanions

金属和类金属硫阴离子的地球化学

• 批准号: 0229387
• 负责人: George Helz
• 金额: --
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229387&HistoricalAwards=false
• 关键词: Geochemistry; Metal; Metalloid; Thioanions

HelzEAR-0229387This project will explore the geochemistry of selected aqueous thioanions. Thioanions consist of a metal or metalloid cation coordinated at least partially by sulfide ions. The chemical behavior of these anions in nature has received little study. The information obtained could have applications in such diverse areas as managing solid (including nuclear) wastes, improving our understanding of ore formation, reconstructing the past redox status of the ocean and healing coastal ecosystems.Using previous studies of Mo behavior in sulfidic waters as a prototype, we will explore mechanisms that trigger particle-association of Re. This element is of interest in paleoenvironmental studies, in geochronology and as a laboratory model of the nuclear waste component, Tc. In oxic environments, the stable form is strongly hydrophilic ReO4-. In suboxic to anoxic environments, Re becomes particle-associated. Mechanisms that could trigger this change in behavior include transformation to thioperrhenates or reduction to ReIV complexes. The nature of the products formed and equilibrium constants characterizing such changes are the objective of this portion of the project.Thiomolybdate ions have been observed to dissolve very insoluble Fe minerals, like pyrite. Formation of strong Fe-Mo-S complexes is implied. We will study this phenomenon systematically in order to characterize the dissolved complexes. If such complexes are capable of reversible equilibrium with pyrite, then they may catalyze formation of this mineral from Fe monosulfide. Mechanisms of pyrite formation remain an area of active interest (and some dispute) among geochemists, despite considerable previous work. Our discovery of very strong complexing between CuI and the oxythioarsenite ion, AsS(OH)(SH)-, has sparked interest from theorists and led to predictions of similarly strong thioarsenite complexes involving other potentially hazardous metals (e.g. Pb2+, Hg2+). We will test these predictions. Complexes of this kind result in synergistic co-transport of hazardous metals and metalloids. They should be accounted for in computational models used for designing hazardous waste sites and making decisions about disposal options for dredge spoil, mine tailings, etc.

该项目将探索选定的水中硫阴离子的地球化学。硫阴离子由至少部分由硫化离子配位的金属或类金属阳离子组成。这些阴离子在自然界中的化学行为很少得到研究。所获得的信息可以应用于各种领域，如管理固体（包括核）废物，提高我们对矿石形成的理解，重建海洋过去的氧化还原状态和修复沿海生态系统。以以往对含硫水体中Mo行为的研究为原型，我们将探索触发Re粒子关联的机制。这种元素在古环境研究、地质年代学和核废料成分的实验室模型中都很有意义。在氧环境中，稳定的形式是强亲水性的ReO4-。在缺氧到缺氧的环境中，Re变成颗粒相关的。可能引发这种行为变化的机制包括转化为硫过酸盐或还原为ReIV复合物。形成的产品的性质和表征这些变化的平衡常数是项目这一部分的目标。硫钼酸盐离子已被观察到溶解非常难溶的铁矿物，如黄铁矿。强Fe-Mo-S配合物的形成是隐含的。我们将系统地研究这一现象，以表征溶解配合物。如果这种配合物能够与黄铁矿可逆平衡，那么它们可能催化单硫化铁生成这种矿物。黄铁矿形成的机制仍然是地球化学家积极感兴趣（和一些争议）的领域，尽管有相当多的前期工作。我们发现崔和氧硫代亚砷酸盐离子as (OH)(SH)-之间有很强的络合作用，这引起了理论家的兴趣，并导致了类似的强硫代亚砷酸盐络合物涉及其他潜在危险金属（如Pb2+， Hg2+）的预测。我们将检验这些预测。这种配合物导致有害金属和类金属的协同共输。在设计危险废物场址和决定疏浚废物、矿山尾矿等的处置办法时所使用的计算模型中应考虑到这些因素。